Electrical and Computer Engineering

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This is the collection for the University of Waterloo's Department of Electrical and Computer Engineering.

Research outputs are organized by type (eg. Master Thesis, Article, Conference Paper).

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Now showing 1 - 20 of 2024

Convex Optimization and Utility Theory: New Trends in VLSI Circuit Layout
(University of Waterloo, 1999) Etawil, Hussein A. Y.
The design of modern integrated circuits is overwhelmingly complicated due to the enormous number of cells in a typical modern circuit. To deal with this difficulty, the design procedure is broken down into a set of disjoint tasks. Circuit layout is the task that refers to the physical realization of a circuit from its functional description. In circuit layout, a connection-list called netlist of cells and nets is given. Placement and routing are subtasks associated with circuit layout and involve determining the geometric locations of the cells within the placement area and connecting cells sharing common nets. In performing the placement and the routing of the cells, minimum placement area, minimum delay and other performance constraints need to be observed. In this work, we propose and investigate new approaches to placement and routing problems. Specifically, for the placement subtask, we propose new convex programming formulations to estimate wirelength and force cells to spread within the placement area. As opposed to previous approaches, our approach is partitioning free and requires no hard constraints to achieve cell spreading within the placement area. The result of the global optimization of the new convex models is a global placement which is further improved using a Tabu search based iterative technique. The effectiveness, robustness and superiority of the approach are demonstrated on a set of nine benchmark industrial circuits. With regard to the routing subtask, we propose a hybrid methodology that combines Tabu search and Stochastic Evolution as a search engine in a new channel router. We also propose a new scheme based on Utility Theory for selecting and assigning nets to tracks in the channel. In this scheme, problem-domain information expressed in the form of utility functions is used to guide the search engine to explore the search space effectively. The effectiveness and robustness of the approach is demonstrated on five industrial benchmarks.
Load Balancing Schemes for Distributed Real-Time Interactive Virtual World Simulations
(University of Waterloo, 2000) Cunningham, Ian Joseph
Over the last several years, there has been tremendous growth in online gaming (i. e. playing games over the internet). The Massively Multiplayer Online Role Playing Game (MMORPG) is one type of online game. An MMORPG is played within a virtual world. Users have an in-game representation, called an avatar, that they control. Typically there are over a thousand avatars in the virtual world at one time. Users use client software to connect to an MMORPG server over the internet. If just one server is used then the number of avatars that can be supported in the virtual world at one time is severely limited. In order to overcome this, a multi-server approach is needed. Unlike traditional load balancing and partitioning schemes, which generally use task partitioning, data partitioning is required in this case. This thesis investigates schemes for partitioning and load balancing MMORPG applications on a network of processors. In particular, three different schemes were developed andexamined. These are: Static Av, Static MS and Dynamic MS. Static Avassigns avatars to each server, one at a time, as they enter thesimulation. Static MS assigns equal sized portions of the map of thevirtual world to each server. An avatar is assigned to the server thatowns the part of the map that the avatar is "standing"on. Dynamic MS divides the map into many more segments than there are servers. The map segments are dynamicallydistributed among the servers based on the results of aload balancing algorithm. The thesis details the algorithms and the performance associated with each of the schemes. In summary, Static Av does not perform well, whereas Static MS and Dynamic MS can be used to parallelize MMORPGapplications. To the best of our knowledge, this is thefirst published work that looks at the issue ofparallelizing and load balancing such applications.
Finite Field Multiplier Architectures for Cryptographic Applications
(University of Waterloo, 2000) El-Gebaly, Mohamed
Security issues have started to play an important role in the wireless communication and computer networks due to the migration of commerce practices to the electronic medium. The deployment of security procedures requires the implementation of cryptographic algorithms. Performance has always been one of the most critical issues of a cryptographic function, which determines its effectiveness. Among those cryptographic algorithms are the elliptic curve cryptosystems which use the arithmetic of finite fields. Furthermore, fields of characteristic two are preferred since they provide carry-free arithmetic and at the same time a simple way to represent field elements on current processor architectures. Multiplication is a very crucial operation in finite field computations. In this contribution, we compare most of the multiplier architectures found in the literature to clarify the issue of choosing a suitable architecture for a specific application. The importance of the measuring the energy consumption in addition to the conventional measures for energy-critical applications is also emphasized. A new parallel-in serial-out multiplier based on all-one polynomials (AOP) using the shifted polynomial basis of representation is presented. The proposed multiplier is area efficient for hardware realization. Low hardware complexity is advantageous for implementation in constrained environments such as smart cards. Architecture of an elliptic curve coprocessor has been developed using the proposed multiplier. The instruction set architecture has been also designed. The coprocessor has been simulated using VHDL to very the functionality. The coprocessor is capable of performing the scalar multiplication operation over elliptic curves. Point doubling and addition procedures are hardwired inside the coprocessor to allow for faster operation.
A Study of the Automatic Speech Recognition Process and Speaker Adaptation
(University of Waterloo, 2000) Stokes-Rees, Ian James
This thesis considers the entire automated speech recognition process and presents a standardised approach to LVCSR experimentation with HMMs. It also discusses various approaches to speaker adaptation such as MLLR and multiscale, and presents experimental results for cross-task speaker adaptation. An analysis of training parameters and data sufficiency for reasonable system performance estimates are also included. It is found that Maximum Likelihood Linear Regression (MLLR) supervised adaptation can result in 6% reduction (absolute) in word error rate given only one minute of adaptation data, as compared with an unadapted model set trained on a different task. The unadapted system performed at 24% WER and the adapted system at 18% WER. This is achieved with only 4 to 7 adaptation classes per speaker, as generated from a regression tree.
Inorganic Phosphor Coatings for Ultraviolet Responsive Image Detectors
(University of Waterloo, 2000) Franks, Wendy
Typical CCD digital imaging sensors are insensitive to ultraviolet ( UV ) radiation by virtue of the very shallow ( 2 nm ) penetration depth in silicon. This warrants the use of a post-packaging coating to up-covert the UV radiation to longer wavelengths. In this thesis, A light-converting inorganic coating has been developed to improve the responsivity of gated CCD image sensors in the UV ( from 250 - 400 nm ). The coating consists of a plastic acrylic layer doped with inorganic phosphors. The coating is deposited using a spin-coater typically used by the IC fabrication industry. Inorganic phosphors were selected over organic phosphors since they are quite well established and are typically used to coat light bulbs, an application that requires a long lifetime. In contrast, organic phosphors rapidly degrade upon exposure to UV radiation. The parameters associated with the coating and coated sensor are presented here. They include coating conversion effciency, penetration depth, photostability; and coated sensor quantum effciency, contrast transfer function and photo-response non-uniformity. The coatings presented here are a viable, cost-effective alternative to other UV response CCD designs.
Analysis and Design of Lossless Bi-level Image Coding Systems
(University of Waterloo, 2000) Guo, Jianghong
Lossless image coding deals with the problem of representing an image with a minimum number of binary bits from which the original image can be fully recovered without any loss of information. Most lossless image coding algorithms reach the goal of efficient compression by taking care of the spatial correlations and statistical redundancy lying in images. Context based algorithms are the typical algorithms in lossless image coding. One key probelm in context based lossless bi-level image coding algorithms is the design of context templates. By using carefully designed context templates, we can effectively employ the information provided by surrounding pixels in an image. In almost all image processing applications, image data is accessed in a raster scanning manner and is treated as 1-D integer sequence rather than 2-D data. In this thesis, we present a quadrisection scanning method which is better than raster scanning in that more adjacent surrounding pixels are incorporated into context templates. Based on quadrisection scanning, we develop several context templates and propose several image coding schemes for both sequential and progressive lossless bi-level image compression. Our results show that our algorithms perform better than those raster scanning based algorithms, such as JBIG1 used in this thesis as a reference. Also, the application of 1-D grammar based codes in lossless image coding is discussed. 1-D grammar based codes outperform those LZ77/LZ78 based compression utility software for general data compression. It is also effective in lossless image coding. Several coding schemes for bi-level image compression via 1-D grammar codes are provided in this thesis, especially the parallel switching algorithm which combines the power of 1-D grammar based codes and context based algorithms. Most of our results are comparable to or better than those afforded by JBIG1.
Analytical Methods for the Performance Evaluation of Binary Linear Block Codes
(University of Waterloo, 2000) Chaudhari, Pragat
The modeling of the soft-output decoding of a binary linear block code using a Binary Phase Shift Keying (BPSK) modulation system (with reduced noise power) is the main focus of this work. With this model, it is possible to provide bit error performance approximations to help in the evaluation of the performance of binary linear block codes. As well, the model can be used in the design of communications systems which require knowledge of the characteristics of the channel, such as combined source-channel coding. Assuming an Additive White Gaussian Noise channel model, soft-output Log Likelihood Ratio (LLR) values are modeled to be Gaussian distributed. The bit error performance for a binary linear code over an AWGN channel can then be approximated using the Q-function that is used for BPSK systems. Simulation results are presented which show that the actual bit error performance of the code is very well approximated by the LLR approximation, especially for low signal-to-noise ratios (SNR). A new measure of the coding gain achievable through the use of a code is introduced by comparing the LLR variance to that of an equivalently scaled BPSK system. Furthermore, arguments are presented which show that the approximation requires fewer samples than conventional simulation methods to obtain the same confidence in the bit error probability value. This translates into fewer computations and therefore, less time is needed to obtain performance results. Other work was completed that uses a discrete Fourier Transform technique to calculate the weight distribution of a linear code. The weight distribution of a code is defined by the number of codewords which have a certain number of ones in the codewords. For codeword lengths of small to moderate size, this method is faster and provides an easily implementable and methodical approach over other methods. This technique has the added advantage over other techniques of being able to methodically calculate the number of codewords of a particular Hamming weight instead of calculating the entire weight distribution of the code.
Executable Model Synthesis and Property Validation for Message Sequence Chart Specifications
(University of Waterloo, 2000) Tysowski, Piotr
Message sequence charts (MSC’s) are a formal language for the speciﬁcation of scenarios in concurrent real-time systems. The thesis addresses the synthesis of executable object-oriented design-time models from MSC speciﬁcations. The synthesis integrates with the software development process, its purpose being to automatically create working prototypes from speciﬁcations without error and create executable models on which properties may be validated. The usefulness of existing algorithms for the synthesis of ROOM (Real-Time Object Oriented Modeling) models from MSC’s has been evaluated from the perspective of an applications programmer ac-cording to various criteria. A number of new synthesis features have been proposed to address them, and applied to a telephony call management system for illustration. These include the speciﬁcation and construction of hierarchical structure and behavior of ROOM actors, views, multiple containment, replication, resolution of non-determinism and automatic coordination. Generalizations and algorithms have been provided. The hierarchical actor structure, replication, FSM merging, and global coordinator algorithms have been implemented in the Mesa CASE tool. A comparison is made to other speciﬁcation and modeling languages and their synthesis, such as SDL, LSC’s, and statecharts. Another application of synthesis is to generate a model with support for the automated validation of safety and liveness properties. The Mobility Management services of the GSM digital mobile telecommunications system were speciﬁed in MSC’s. A Promela model of the system was then synthesized. A number of optimizations have been proposed to reduce the complexity of the model in order to successfully perform a validation of it. Properties of the system were encoded in Linear Temporal Logic, and the Promela model was used to automatically validate a number of identiﬁed properties using the model checker Spin. A ROOM model was then synthesized from the validated MSC speciﬁcation using the proposed reﬁnement features.
Efficient Analysis for Nonlinear Effects and Power Handling Capability in High Power HTSC Thin Film Microwave Circuits
(University of Waterloo, 2000) Tang, Hongzhen
In this study two nonlinear analysis methods are proposed for investigation of nonlinear effects of high temperature superconductive(HTSC) thin film planar microwave circuits. The MoM-HB combination method is based on the combination formulation of the moment method(MoM) and the harmonic balance(HB) technique. It consists of linear and nonlinear solvers. The power series method treats the voltages at higher order frequencies as the excitations at the corresponding frequencies, and the higher order current distributions are then obtained by using the moment method again. The power series method is simple and fast for finding the output power at higher order frequencies. The MoM-HB combination method is suitable for strong nonlinearity, and it can be also used to find the fundamental current redistribution, conductor loss, and the scattering parameters variation at the fundamental frequency. These two proposed methods are efficient, accurate, and suitable for distributed-type HTSC nonlinearity. They can be easily incorporated into commercial EM CAD softwares to expand their capabilities. These two nonlinear analysis method are validated by analyzing a HTSC stripline filter and HTSC antenna dipole circuits. HTSC microstrip lines are then investigated for the nonlinear effects of HTSC material on the current density distribution over the cross section and the conductor loss as a function of the applied power. The HTSC microstrip patch filters are then studied to show that the HTSCinterconnecting line could dominate the behaviors of the circuits at high power. The variation of the transmission and reflection coefficients with the applied power and the third output power are calculated. The HTSC microstrip line structure with gilded edges is proposed for improving the power handling capability of HTSC thin film circuit based on a specified limit of harmonic generation and conductor loss. A general analysis approach suitable for any thickness of gilding layer is developed by integrating the multi-port network theory into aforementioned proposed nonlinear analysis methods. The conductor loss and harmonic generation of the gilded HTSC microstrip line are investigated.
Stabilization of Discrete-time Systems With Bounded Control Inputs
(University of Waterloo, 2000) Jamak, Anes
In this paper we examine the stabilization of LTI discrete-time systems with control input constraints in the form of saturation nonlinearities. This kind of constraint is usually introduced to simulate the effect of actuator limitations. Since global controllability can not be assumed in the presence of constrained control, the controllable regions and their characterizations are analyzed first. We present an efficient algorithm for finding controllable regions in terms of their boundary hyperplanes (inequality constraints). A previously open question about the exact number of irredundant boundary hyperplanes is also resolved here. The main result of this research is a time-optimal nonlinear controller which stabilizes the system on its controllable region. We give analgorithm for on-line computation of control which is also implementable for high-order systems. Simulation results show superior response even in the presence of disturbances.
Mixed signal design flow, a mixed signal PLL case study
(University of Waterloo, 2001) Shariat Yazdi, Ramin
Mixed-signal designs are becoming more and more complex every day. In order to adapt to the new market requirements, a formal process for design and verification of mixed signal systems i. e. top-down design and bottom-up verification methodology is required. This methodology has already been established for digital design. The goal of this research is to propose a new design methodology for mixed signal systems. In the first two chapters of this thesis, the need for a mixed signal design flow based on top-down design methodology will be discussed. The proposed design flow is based on behavioral modeling of the mixed signal system using one of the mixed signal behavioral modeling languages. These models can be used for design and verification through different steps of the design from system level modeling to final physical design. The other advantage of the proposed flow is analog and digital co-design. In the remaining chapters of this thesis, the proposed design flow was verified by designing an 800 MHz mixed signal PLL. The PLL uses a charge pump phase frequency detector, a single capacitor loop filter, and a feed forward error correction architecture using an active damping control circuit instead of passive resistor in loop filter. The design was done in 0. 18- µ m CMOS process technology.
Application of Turbo-Codes in Digital Communications
(University of Waterloo, 2001) Haj Shir Mohammadi, Atousa
This thesis aims at providing results and insight towards the application of turbo-codes in digital communication systems, mainly in three parts. The first part considers systems of combined turbo-code and modulation. This section follows the pragmatic approach of the first proposed such system. It is shown that by optimizing the labeling method and/or modifying the puncturing pattern, improvements of more than 0. 5 dB insignal to noise ratio (SNR) are achieved at no extra cost of energy, complexity, or delay. Conventional turbo-codes with binary signaling divide the bit energy equally among the transmitted turbo-encoder output bits. The second part of this thesis proposes a turbo-code scheme with unequal power allocation to the encoder output bits. It is shown, both theoretically and by simulation, that by optimizing the power allocated to the systematic and parity check bits, improvements of around 0. 5 dB can be achieved over the conventional turbo-coding scheme. The third part of this thesis tackles the question of ``the sensitivity of the turbo-code performance towards the choice of the interleaver'', which was brought up since the early studies of these codes. This is the first theoretical approach taken towards this subject. The variance of the bound is evaluated. It is proven that the ratio of the standard deviation over the mean of the bound is asymptotically constant (for large interleaverlength, N), decreases with N, and increases with SNR. The distribution of the bound is also computationally developed. It is shown that as SNR increases, a very low percentage of the interleavers deviate quite significantly from the average bound but the majority of the random interleavers result in performances very close to the average. The contributions of input words of different weights in the variance of performance bound are also evaluated. Results show that these contributions vary significantly with SNR and N. These observations are important when developing interleaver design algorithms.
CDMA Channel Selection Using Switched Capacitor Technique
(University of Waterloo, 2001) Nejadmalayeri, Amir Hossein
CDMA channel selection requires sharp as well as wide-band Filtering. SAW Filters which have been used for this purpose are only available in IF range. In direct conversion receivers this has to be done at low frequencies. Switched Capacitor technique has been employed to design a low power, highly selective low-pass channel select Filter for CDMA wireless receivers. The topology which has been chosen ensures the low sensitivity of the Filter response. The circuit has been designed in a mixed-mode 0. 18u CMOS technology working with a single supply of 1. 8 V while its current consumption is less than 10 mA.
An Analysis of Wireless High-speed Data Services for Cellular CDMA Systems
(University of Waterloo, 2002) Chan, Kwong Hang Kevin
The interest in the development of wireless high-speed data services is in response to the strong market demand for high-speed wireless Internet access. Current standards aim at delivering a peak data rate greater than 2Mbps on the forward link. Since data services and voice services are fundamentally different, new concepts were introduced in the design of the forward data channel. In addition, methods of evaluating the performance of a cellular CDMA system have to be revisited. This thesis proposes a method which can be used to find the forward link peak and average data rates, throughput and coverage of a cellular CDMA system which is capable of delivering high-speed wireless data. A summary of changes in design philosophy and recent advances in technologies which enable high-speed wireless data delivery are presented. The proposed method takes into account major aspects commonly found in the forward data channel and applies the generalized Shannon capacity formula for multi-element antenna (MEA) systems. The analysis focuses on the physical layer and is flexible enough to be adapted to various propagation environments, antenna configurations, multicode allocations, user distributions and cell site configurations. Sample numerical results for various multicode allocations are shown using a system model with two-tier interfering cells with one transmit antenna and two receive antennas operating under a frequency selective slow fading channel with propagation environment described by the Recommendation ITU-R M. 1225 indoor office, outdoor to indoor and pedestrian and vehicular test environments. Different transmit / receive antenna configurations and multicode allocations and their impact on the average data rate is also explored.
Circuit Model Parameter Extraction and Optimization for Microwave Filters
(University of Waterloo, 2002) Busuioc, Dan
This thesis presents a method for parameter extraction of circuit elements from microwave filters. This diagnosis method can be applied to a sufficiently large number of filters and it can also be used in conjunction with a neural network model for filter design, greatly reducing development time. This thesis is an introduction of parameter extraction and circuit modelling through use of neural networks. It also presents an implementation of the proposed method as well as numerical results and validation data. Detailed implementation code is presented in the appendix.
Phosphor Coated UV-Responsive CCD Image Sensors
(University of Waterloo, 2002) Alexander, Stefan
Typical CCD image sensors are not sensitive to Ultra-Violet (UV) radiation, because the UV photons have a penetration depth of 2nm in the ~1µm thick polysilicon gate material. An inorganic phosphor coating was developed previously (by Wendy Franks et al [1, 2]) that was shown to be a viable solution to creating a UV-sensitive CCD image sensor. The coating absorbs incident UV radiation (250nm) and re-emits it in the visible (550-611nm) where it can penetrate the gate material. This coating was deposited using a settle-coat type deposition. Improved coating techniques are presented here. These include a commercial coating from Applied Scintillation Technologies (AST), a Doctor-Blade coating, e-beam deposition, and laser ablation. The properties of the coating, and of the coated sensors are presented here. Tests performed on the sensors include Quantum Efficiency, Photo-Response Non-Uniformity, Contrast Transfer Function, and Lifetime. The AST coating is a viable method for commercial UV-responsive CCD image sensors. The Doctor-Blade coatings show promise, but issues with clustering of the coating need to be resolved before the sensors can be used commercially. E-beam deposition and laser ablation need further research to provide a viable coating.
Split-Domain TCP-Friendly Protocol For MPEG-4 Adaptive Rate Video Streaming Over 3G Networks
(University of Waterloo, 2002) Ha, Rick Wan Kei
The imminent inception of third-generation (3G) mobile communication networks offers an unprecedented opportunity for the development of video streaming applications through wireless Internet access. Different design challenges exist in implementing video streaming connections spanning both wired and wireless domains. A split-domain TCP-friendly streaming video transmission protocol is presented based on adaptive rate encoding in the MPEG-4 video format. Network simulations are conducted to demonstrate the benefits and viability of such a video streaming scheme over existing options. Further feature enhancements and refinements are necessary for the proposed protocol to achieve its full potential.
Foveated Stereo Video Compression for Visual Telepresence
(University of Waterloo, 2002) Fok, Stanley
This thesis focuses on the design of a foveated stereo video compression algorithm for visual telepresence applications. In a typical telepresence application, a user at the local site views real-time stereo video recorded and transmitted from a robotic camera platform located at a remote site. The robotic camera platform tracks the user's head motion producing the sensation of being present at the remote site. The design of the stereo video compression algorithm revolved around a fast spatio-temporal block-based motion estimation algorithm, with a foveated SPIHT algorithm used to compress and foveate the independent frames and error residues. Also, the redundancy between the left and right video streams was exploited by disparity compensation. Finally, position feedback from the robotic camera platform was used to perform global motion compensation, increasing the compression performance without raising computation requirements. The algorithm was analysed by introducing the above mentioned components separately. It was found that each component increased the compression rate significantly, producing compressed video with similar compression and quality as MPEG2. The implementation of the algorithm did not meet the real-time requirements on the experiment computers. However, the algorithm does not contain any intrinsic delays. Therefore, given faster processors or optimized software implementation, the design should be able to run in real-time.
Radio Resource Management for Cellular CDMA Systems Supporting Heterogeneous Services
(University of Waterloo, 2002) Zhao, Dongmei
A novel radio resource management (RRM) scheme, which jointly considers the system characteristics from the physical, link and network layers, is proposed for cellular code division multiple access (CDMA) systems. Specifically, the power distribution at the physical layer distributes only the necessary amount of power to each connection in order to achieve its required signal-to-interference-plus-noise ratio (SINR). The rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness of the packet generation process. At the link layer, a packet scheduling scheme is developed based on the information of power distribution and rate allocation from the physical layer to achieve guaranteed quality of service (QoS). It schedules the system resource on a time slot basis to efficiently utilize the system resource in every time slot and to improve the packet throughput for non-real-time traffic. A connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed at the network layer. The CAC scheme also makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service (GOS) performance, in terms of new connection blocking probability (NCBP), HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.
Design and Analysis of Intelligent Fuzzy Tension Controllers for Rolling Mills
(University of Waterloo, 2002) Liu, Jingrong
This thesis presents a fuzzy logic controller aimed at maintaining constant tension between two adjacent stands in tandem rolling mills. The fuzzy tension controller monitors tension variation by resorting to electric current comparison of different operation modes and sets the reference for speed controller of the upstream stand. Based on modeling the rolling stand as a single input single output linear discrete system, which works in the normal mode and is subject to internal and external noise, the element settings and parameter selections in the design of the fuzzy controller are discussed. To improve the performance of the fuzzy controller, a dynamic fuzzy controller is proposed. By switching the fuzzy controller elements in relation to the step response, both transient and stationary performances are enhanced. To endow the fuzzy controller with intelligence of generalization, flexibility and adaptivity, self-learning techniques are introduced to obtain fuzzy controller parameters. With the inclusion of supervision and concern for conventional control criteria, the parameters of the fuzzy inference system are tuned by a backward propagation algorithm or their optimal values are located by means of a genetic algorithm. In simulations, the neuro-fuzzy tension controller exhibits the real-time applicability, while the genetic fuzzy tension controller reveals an outstanding global optimization ability.

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